WORK PLANS - Laserfiche WebLink

Home Browse Search

Frontier Transportation, Inc. 425 Larch Road Site Assessment Work Plan May 6, 2005 ' Page 3 MW- 15 using EPA Method 8260B . No other oxygenates or lead scavengers were detected. The maximum TPH-gas detected was 1 .7 mg/kg at 10' bgs in MW- 15 using EPA Method 8015M. No detectable BTEX was identified in the soil column for MW45 through MW- 18 . See Figure 2 for well locations. 30) SITE GEOLOGY/HYDROGEOLOGY l The site is located on the boundary of the Sacramento Valley and the San Joaquin Valley within the west-central portion of the Great Valley Geomorphic province of California. The Great Valley has been filled with a sequence of older to younger alluvium of Pliocene to Holocene age which overlay sedimentary rocks of Cretaceous to Tertiary age. These sedimentary I units, in turn, overlay a crystalline basement of Paleozoic and Mesozoic metamorphic and igneous rocks. The shallow subsurface geology in the site vicinity is a heterogeneous mix of gravel, sand, silt, and clay (Reference; Site Characterization Report, Twining Laboratories, October 16, 1996). BEII encountered predominantly clays with some silts and sands from 0' to 40' bgs during well advancement. First subsurface water was encountered at depths from .l l to 1Z bgs during tank removal and monitoring well installation at this site in 1995 and 1996. Since then, shallow subsurface water has been encountered between 6' and 10' bgs. The flow of groundwater is generally in a western direction beneath the site (See Figure 3 , Groundwater Gradient Map) . C 4.0) PROPOSED SCOPE OF WORK 1 The extent of the MTBE contaminant plume is not clearly defined to the west of the shop based on current data so BEA proposes the installation of three (3) additional wells. Each well will be advanced to a total depth of 20 ' below grade surface (bgs) with the screen interval between 5 ' bgs and 20' bgs. (See Figure 2 for proposed well location). The analytical data from the soil and groundwater samples at the new shallow wells will be significant in defining the { boundary of the contaminant plume. 5.0) GROUNDWATER WELL INSTALLATION i f A hollow stem auger drill rig will be used to provide the soil borings for well installation. Drillers will hold a California t to C-57 contractor's license. Typical auger size for the well installation described below is i h outside diameter and 6-inch inside diameter. The borings � rbw"" Y f �